Nanostructure Engineering Significantly Enhances Capacitive Energy Storage Performance in All-Polymer Dielectrics at Elevated Temperatures

The growing demand for electrostatic capacitors in high-temperature environments requires dielectric polymers capable of withstanding both elevated temperatures and high electric fields. Here, we investigate all-polymer nanodielectrics (PNDs) fabricated through polymerization-induced microphase separation (PIMS) in thermoplastic/thermoset blends, focusing on the role of thermoset resins in high-temperature capacitive performance. Two BMI monomers, 2,2-bis(4-(4-maleimidophenoxy)phenylpropane) (BMP) and 4,4'-bismaleimidodiphenylmethane (BDM), form cross-linked domains of different sizes in a polysulfone (PSU) matrix, creating deeper charge traps. While trap depths are similar, PSU/BMP PNDs exhibit higher trap density owing to smaller BMP domains resulting from enhanced compatibility with PSU. This reduces current density at high temperatures compared to PSU/BDM and pristine PSU. Consequently, PSU/BMP PNDs demonstrate superior capacitive energy storage at elevated temperatures. These findings emphasize the importance of interfacial area in determining high-temperature electrical properties and provide insights for designing nanostructured all-polymer dielectrics for advanced applications.